Understanding fusion dynamics of metallic powders and powder-substrate interactions is important for reducing the defects, and thus improving surface and bulk quality of additive manufactured (AM) parts. Albeit recent advances in AM technology, there is a great need of theoretical analysis at the powder level to quantify and predict relevant mesoscale dynamics in the manufacturing process. We present a thermodynamically consistent phase-field modeling framework to integrate relevant thermal fluid phenomena and elastic structure response, including phase transition, thermal capillarity, interfacial deformation, and thermal stress induced by spot laser heating. The 2D results show that the fusion of pure titanium powder and titanium substrate can be significantly enhanced by the capillary effect when the partially melted powder is bridging the molten substrate, whereas the thermal-elastic deformation has a longer range effect, which is primarily influenced by the heating power of the laser beam. (C) 2018 Elsevier Ltd. All rights reserved.